I've been looking at a new Ubuntu LTS-based OS that uses the Xfce desktop but is designed especially for older hardware (unlike Xubuntu now), called Linux Lite:
And one the things that really attracts me to it is the way they have adapted it for new users. The menu, for example, has names that make sense: "File Manager" instead of "Thunar," for example. A new user wouln't have any idea what "Thunar" is, but a file manager is a file manager. The whole menu is like that.
Very lightweight, LTS-reliable, familiar Xfce interface, Steam preinstalled (!!!), easy on the eyes and the hardware. Definitely worth a look!